·imUnek J., BartoAova H.: Effect of dietary chitin and chitosan on cholesterolemia of rats. Acta Vet. Brno 2005, 74: 491-499. Chitin – chitosan is being advertised as a food supplement that effectively lowers blood cholesterol concentration and controls obesity. The lard-fed rat was chosen because this model shares similarities with human hypercholesterolemia. The male rats were divided into six groups (A-F), each with 6 rats, and fed 6 weeks ad libitum diets prepared on base of commercial diet by addition of lard (diets D, E F), cholesterol (diet C), chitin (diets B, C, D) and chitosan (diet F). There were no significant differences in weight gain and feed efficiencies in all groups during experimental period. The histology examination of liver slices revealed the most pronounced periacinal (3.0) and centroacinal (1.3) steatosis in animals of the group C. In the F group was detected small periacinal steatosis only. The total serum cholesterol level was significantly increased (P < 0.05) in rats fed high fat diets (D, E, F; 2.21 ± 0.15, 2.25 ± 0.16, 2.27 ±0.23 mmol·l-1) and C group (2.16 ± 0.56 mmol·l-1) in comparison with control group (1.57 ± 0.26 mmol·l -1 ) and group B (1.68 ± 0.09 mmol·l -1 ). Similarly HLD-cholesterol levels were in groups B, C, D, E and F increased (1.02 ± 0.05, 0.90 ± 0.18, 1.30 ± 0.18, 1.34 ± 0.11 and 1.38 ± 0.24 mmol·l -1 , resp.). While the cholesterol content in liver homogenates was significantly higher in animals fed cholesterol-rich diet (8.79 ± 0.50 mmol·g-1, P < 0.05), chitosan addition significantly depressed the cholesterol concentration (5.76 ± 0.95 mmol.g-1, P < 0.05). Faecal cholesterol excretion was greatest in the rats of C group (13.63 ± 2.93 mmol.g -1 , P < 0.05). Also faeces of the animals fed the lard-enriched diets contained nonsignificantly more cholesterol than animals of control group. This effect seems to be reinforced by chitosan component in diet F. According to our results 5% chitin and/or chitosan addition have not prevented any increase in liver weight or the level of plasma cholesterol and also have not reduced the liver cholesterol content in rats fed enriched lard diet. In presence of chitosan higher excretion of faecal cholesterol and lipids were found. Chitin/chitosan, dietary hypercholesterolemia, rats